Doesn't that mean the US wasn't allowed to do any such operation?

Allowed by whom? There is no world police.

If the United States government decides to assassinate someone, they do not need anybody's permission. They won't commit drone strikes on friendly countries without coordination, or unfriendly countries that might strike back. Not because of whether it's allowed or not, but because they would have to face with the consequences. That's why they assassinate people with drone strikes in Yemen, Afghanistan, or Somalia, but not in Russia or the United Kingdom. They target weak enemies this way, but not friends or strong enemies, because there would be a high price to pay.

Doesn't that mean the US wasn't allowed to do any such operation?

Allowed by whom? There is no world police.

If the United States government decides to assassinate someone, they do not need anybody's permission. They usually won't commit drone strikes on friendly countries without coordination, or unfriendly countries that might strike back. Not because of whether it's allowed or not, but because they would have to face with the consequences. That's why they assassinate people with drone strikes in Yemen, Afghanistan, or Somalia, but not in Russia or the United Kingdom. They target weak enemies this way, but not friends or strong enemies, because there would be a high price to pay.

Doesn't that mean the US wasn't allowed to do any such operation?

Allowed by whom? There is no world police.

If the United States government decides to assassinate someone, they do not need anybody's permission. They won't commit drone strikes on friendly countries without coordination. Not because of whether it's allowed or not, but because they would have to face with the consequences. That's why they assassinate people with drone strikes in Yemen, Afghanistan, or Somalia, but not in Russia or the United Kingdom. They target weak enemies this way, but not friends or strong enemies, because there would be a high price to pay.

Doesn't that mean the US wasn't allowed to do any such operation?

Allowed by whom? There is no world police.

If the United States government decides to assassinate someone, they do not need anybody's permission. They won't commit drone strikes on friendly countries without coordination, or unfriendly countries that might strike back. Not because of whether it's allowed or not, but because they would have to face with the consequences. That's why they assassinate people with drone strikes in Yemen, Afghanistan, or Somalia, but not in Russia or the United Kingdom. They target weak enemies this way, but not friends or strong enemies, because there would be a high price to pay.